The present invention relates generally to bearing housings and, more particularly, to bearing housings including proximity probes for sensing the relative vibration and position of a rotating shaft contained therein.
As referred to herein, a bearing assembly is used to describe a device that supports a rotating, sliding, or oscillating member and that reduces friction therebetween. In one exemplary type of bearing assembly, known as a journal or sleeve bearing assembly, a cylindrical shaft or journal is supported in a stationary device known as the bearing. In a journal bearing, an oil film may be interposed between a shaft and a cylindrical shell. The shell is often referred to as a bushing, sleeve, or brass.
As referred to herein, a journal bearing can be hydrodynamic or hydrostatic. In hydrodynamic bearings, when a shaft is rotated within the bearing assembly, a flow of oil between the shaft and the shell generates pressure sufficiently high to support the load of the shaft. Hydrostatic bearings operate similarly except that externally supplied pressure is applied to the oil film in order to support the load. Hydrostatic bearings are typically used when loads are too high or speeds are too low for the self-generated interior oil film pressure to support the shaft load.
Ideally, in journal bearings, the friction between the shaft and the cylindrical shell, which is related to the viscosity of the lubricant, is small because metal to metal contact does not exist. Also, in ideal conditions, the rotating shaft is held steady within the bearing assembly. Costly failures can occur when the shaft becomes unbalanced, misaligned, or damaged.
In the past, certain types of stand alone proximity probes have been utilized to monitor shaft vibration and location for preventing costly failures and for indicating abnormalities in the proper operation of the bearing assembly. In prior applications, the proximity probes were installed by drilling and threading a hole through the bearing housing. In order to position and protect the probes, a rigid, metal housing assembly was placed in the drilled hole which surrounded the proximity probes and any wires connected thereto. The housing assembly included a top housing portion which was threaded into the bearing housing. A metal sleeve then extended from the bearing housing to a rotatable shaft contained therein.
The prior art method of installing proximity probes in journal bearings has several disadvantages. First, the cost of the probe housing assembly together with the cost of installation can comprise a very expensive package. Also, it is difficult to adjust the proximity probe in relation to the rotating shaft. During operation, the probe should remain adjacent and close to the shaft without ever contacting or touching it. In the prior art device, this gap between the probe and the shaft is difficult to adjust because the probe housing assembly is mounted to and adjusted from the outside bearing housing instead of an inside cylindrical shell. Further, because the probe housing assembly is mounted to the outside bearing housing, the probe measures shaft vibration relative to the bearing housing and not relative to the cylindrical shell which may create errors in the measurement.